A polyvinyl alcohol-based resin (hereinafter, polyvinyl alcohol is often abbreviated to PVA) has hitherto been advantageously used as a dispersion stabilizer in emulsion polymerization of a vinyl acetate-based monomer and an acrylic-based monomer.
Furthermore, various modified PVA-based resins are being investigated for the purpose that the aqueous emulsion obtained is improved in mechanical stability, freezing stability, and high-temperature standing stability. For example, such aqueous emulsions which have been proposed include: an aqueous emulsion comprising a PVA-based polymer having a mercapto group at a molecular end, a surfactant, and a polymer mainly comprising an ethylenically unsaturated monomer unit and having an average particle diameter of 0.3 μm or less (see, for example, patent document 1); an aqueous emulsion in which a PVA-based resin having a block character [η] of more than 0.6 and a degree of saponification of more than 95.0% by mole and having an active hydrogen in the molecule is adhered to the surface of the polymer particle (see, for example, patent document 2); and an acrylic-based copolymer emulsion obtained by using an amide-modified PVA as a protective-colloid stabilizer (see, for example, patent document 3).    Patent Document 1: JP-A-2003-171567    Patent Document 2: JP-A-2003-277419    Patent Document 3: JP-A-2004-018692